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Understand your email

SMTP diagnostics

Check connectivity, SMTP capabilities and the TLS certificate. Get a clear server configuration report.

Start a check

Free diagnostics

Start a check

My history

Port 25: we find the receiving server using MX. For 465 or 587, enter the exact submission hostname from your mail settings. No password needed.

Checks that help

Find the cause of mail connection issues

SMTP diagnostics checks whether a mail server responds and supports a secure connection. Use it after moving email services, changing settings or encountering sending errors in a website, CRM or email application.

  1. 01

    Choose what to check

    For incoming mail, enter the domain and port 25. For outgoing mail, use the server and port from your mail settings.

  2. 02

    Test the connection

    We check the server response and connection security. No email password is needed.

  3. 03

    Review the findings

    If an issue appears, review your settings or share the findings with your administrator.

Your archive

Check history

Reports are saved for 24 hours.

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General iT is here to help

Found an issue? We can help.

Find help for your task, from server configuration to website and CRM notifications.

01

Server support

Get help with your mail server, its configuration and reliable operation.

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Integrations and services

Connect your website, CRM and services so notifications and data reach their destination.

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Virtual servers

Choose resources for your project and discuss its hosting requirements.

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Learn more at your own pace

Explore articles about websites, infrastructure and running online projects on our blog.

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The bigger picture

Continue your checks

The address, server and message affect different stages of delivery. Check the parts that matter to your task.

Questions and answers

What to know

Which port should I choose: 25, 465 or 587?

Port 25 is suitable for checking a domain’s receiving mail server. Applications commonly use 465 or 587 for submission; use the exact hostname and port provided by your mail provider.

Do I need to enter a username and password?

No. The check runs without logging into a mailbox or sending a message. It does not validate your account credentials.

Why could the connection not be established?

The hostname or port may be incorrect, external connections may be restricted, or the server may be temporarily unavailable. Compare your settings with the provider’s instructions. If the issue persists, share the findings with your administrator.

How long is the result available?

Your report is available in your history for 24 hours. You can delete it earlier if you wish.

What online SMTP diagnostics checks

SMTP is used to transfer email. Connection problems can disrupt order confirmations, notifications and business correspondence. This check shows whether the server can be reached, responds to requests and supports a secure connection. When encryption is used, the server certificate is validated. The result helps narrow down the cause before reviewing application settings.

When SMTP works but messages still do not arrive

A working connection is only part of the delivery path. An application may use incorrect credentials, a sender may be blocklisted or the message itself may trigger a filter. This check does not log into a mailbox or send a test message. If connectivity is fine, check the recipient address, the sender IP and a real message using the spam test.